Rheostat.



No. 774.460. PATENTED NOV. 8.; 1904. IVI. WADDELL.

RHEOSTAT.

l APPLIOATION FILED Nov. 25. 190s. No MODEL, s SHEETS- SHEET 1.

No. 774,460. PATENTED NOV. 8, 1904..

M. WADDBLL.

RHEOSTAT.

l APPLIOATION FILED Nov. 25, 1903. No MODEL. a SHEETS-SHEET z.

fg?. L3.

MMM

No. 774,460. PATENTED Nov. 8,1904.

. M. vr ADDELL,

RL .OST/AT.

APPLIOATIO? SILED NOV. 25, 1903.

' N0 MODEL. 3 SEEETS- SHEET 3.

I I. M

'patented November e, 1904,.)

PATENT OEETCE.

MONTGOMERY I/VADDELL, OF NEW YORK, N. Y.

RHEosTAT.

SPECIFICATION forming part of Letters Patent No. 774,460, dated November 83 1904.

Application filed November 25, 1903. Serial No. 182,576. (No model.) i

i To /LZZ whom, t may concern:

Be it known that I, MONTGOMERY WADDELL, a subject of the King of Great Britain, residing in the city, county, and State of New York, have invented a certain new and useful Improvement in Rheostats, of which the following is a specification.

This invention has relation to that class of rheostats which depend for their operation upon changes in relative positions or mutual pressures of conducting elements of high resistance. The most familar example of this type of rheostat is found in those cases Wherein the current is passed ,through a number of pieces of carbon in series and wherein changes of resistance are attained by exerting more or less pressure upon the series ofv carbon elements.

One object of the present invention is the production of a rheostat of the class first above mentioned which may be applied successfully to the regulation of electric currents of much greater quantity than has hitherto been possible and without the generation of undue heat.

Another object of the present invention is the provision of a form of rheostat composed of semiconducting elements, whether of carbon or otherwise, so arranged that the weight of each element orl of each element and its associated parts shall be availed of as a factor in the problem of regulation. As preferably employed this is so accomplished that the weight of each element is brought into play successively, and when so brought into play becomes effective throughout the whole series of elements used.

Another object of this invention is the provision of a rheostat of the type first above mentioned wherein by a suitable modification of successive contact-faces in the resist-r ing elements a progressive change of conductivity can be produced represented by almost any desired curve.

Broadly speaking, the above objects are attained either singly or together by the application either alone or simultaneously of two novel principles of construction and arrangement. The first of these involves the useY of movable resistance-bodies capable of being brought into contact under greater or less pressure and arranged in multiple arc with each other in the circuit to be controlled. The second novel arrangement involves the use of resistance-bodies designed to be brought in contact, whether in multiple arc or series, in such a manner that in the position corresponding to the greatest total resistance imperfect contact or actual separation of successive bodies is insured by mechanical means, and as the total resistance is gradually lowered one after the other of the resistancebodies is removed from the influence of the mechanical separating agent, so that its pressure (due to gravity or any other agency) becomes available for making better contact between all successive resistance-bodies on the side from which pressure is exerted for operating the rheostat.

Certain preferred forms of this invention are illustrated in preferred arrangements in the accompanying drawings, wherein- Figure l is afront view of one form of this rheostat used in connection with an improved automatic regulator. Fig. 2 is a larger front view of a portion of the rheostat shown in Fig. l, showing details. Fig. 3 is an end view of one element. Fig. l is a top View of one element. Fig. 5 is a perspective view of the supporting means for the resistance-bodies preferably employed for the production of a certain desirable curve of conductivities, and Figs. 6 and 7 are side views of parts of two resistance-columns comprising two different kinds of resistance-buttons conforming to my invention.

In Figs. 1 and 2 there is shown a series of carbon buttons which may be placed vertically or in any other position for use as a rheostat. In the form as shown it will be assumed that vthe column of carbon buttons isA vertical. In this form the supporting means consists of two parallel rods l and 2, upon which are threaded supports for successive carbon buttons 3, together with spacingblocks 4, which are threaded over the rods l and 2 in order to preserve the proper positions of the successive supports to the carbon buttons. 2, spacing-blocks 4, and the immediate supports 'for the carbon buttons are all made of metal, and this form is adapted to the use of the buttons in multiple arc. I'Vhere it is desired to use the buttons in series, appropriate changes for purposes of insulation between supports will be supplied by those skilled in the art. The supports and spacing-blocks are all firmly fixed in position by means of the clamping-nuts 5 and 6, which screw over the threaded ends of the rods l and 2, as shown in Fig. 1.

Figs. 2 to show details of arrangement of the carbon buttons and their supports. As here shown, a rest is supplied in the form of a metallic plate 7, bent at right angles and preferably having notches cut into the sides of the upturned edge, as shown at 8. These notches form shoulders which, together with the longer projection between them, afford at once a guide and a rest for the button-supporting springs. The horizontal portion of the plate 7 is cut out in any desired manner, as by an open slot 9, so as to lit over one of the rods l and 2, as shown in Figs. 2 and 4. Riveted or otherwise secured to the plate 7 are two long and very flexible springs 10, curved back upon themselves so as to project forward over the shoulders 8, as clearly shown in Figs. 2 to 5. These springs are the immediate su pports for the carbon buttons or other resistance-buttons, simple or composite, which are employed in the complete rheostat. rIhe springs l0 are used for theiryieldingquality and should be made to oppose as little resistance to movementof the resistances as possible. In the preferred form shown two ends of the springs 10 are turned down on a right angle and perforated, as shown at 11. rI`he side of the carbon button or other resistance-body 3 is placed against these turned-down ends and secured thereto by a screw or rivet. In the preferred form shown clamping-weights l2 and 18 are used,which run the entire length of the carbon button and are so placed that they clamp the button 3 between them and against the turned-down ends of the springs 10. This clamping action is preferably secured by means of the screws 14, threaded into the clamping-weight 13. As thus arranged it will be seen that the plates 7 and springs l0 support successive resistance-bodies at any desired distance apart, the weight of the resistance-body being capable of resting upon the shoulders 8 on the upturned edge of the plate 7. In practice these devices are placed one next to the other and in the vertical form one over the other in such a relative location that successive resistance-bodies are almost always in contact when the springs 10 rest upon the shoulders 8. If contact exists in this position, it should be so light as to produce a very high resistance at the point where the bodies touch. With the resistance-bodies in this posi- In the form shown the rods l and l tion the terminals of a circuit to be controlled may be brought into opposite relation with the column either by connecting the terminals to the two ends for series operation of the rheostat or by connecting the terminals to the two supporting-rods 1 and Q in the form hitherto shown and' described, in which case multiple-arc operation will be accomplished. In either arrangement the position of the resistance-bodies above described, wherein the supporting-springs l0 rest on the shoulders 8, will correspond to the highest degree of resistance which the rheostat is intended to oppose. In order to lower this resistance, whether in series or multiple are, pressure is gradually applied at one end of the column in such a direction as to tend to remove the springs lO from the shoulders 8. In the vertical form shown this pressure will be applied to the bottom of the column. The result of this gradual application of pressure is first to lift the iirst or lowermost of the resistancebodies, together with any weight or weights attached thereto, thus bringing into play the weight so lifted in opposition to the operating force applied and at the same time lowering the contact resistance between this first resistance-body and the next. As the vforce increases the second resistance-body and associated weights will be lifted, and the total force opposed to the operating pressure will be the sum of the two resistance elements and their weights. At the same time the contact resistance between the first and second resistance-bodies will be further decreased by the pressure due to the weight of the second resistance-body and its weights, and there will be an initial lowering of resistance at the contact between the second and third resistancebodies. In the same manner the gradual increase in operating pressure will be opposed by a corresponding increase in available weight of resistance-bodies as the successive bodies are lifted from their rests, and the weight of each resistance-body as it is lifted from its rest will become available at every contact below it or between it and the bearing force for increase of conductivity at such contact. IVhere carbon buttons are used, the effect of increased pressures at the contactsurfaces will of course be to produce a very marked change in resistance, as well at these surfaces as throughout the body of the buttons themselves. There the multiple-arc arrangement of resistance-bodies is used, any change in resistance is due both to the bringing in of new semiconducting bodies in multiple are and to the changes in contact resistance.

It will be seen that there is a very important advantage in this form of movable resistance-rheostat as over the ordinary column of series of carbon buttons subjected to pressure. This .advantage rests principally in the fact that the separate self-supporting carbon but- IOO IIO

tonsor resisting-buttons usedY in this invention, being lifted one by one and thus brought successively into play, exert a uniform increase of mechanical resistance to the operating force, and thus insure aI calculable and constant variation in resistance as the operating force or pressure is increased or decreased through any predeterminedrange. A further advantage of this arrangement lies in the fact that the range or scope of change isimmensely increased, since it only depends on the number of resistance -bodies or carbon buttons used. This is especially true in the multiple-arc arrangement. In the ordinary carbon-button column changes in resistance are not uniform; but even when the column is first used such changes decrease rapidly with the increase of pressure applied. After a column of carbon resistances of the common type has been in use for some time the pressure and the passage of current so effects the carbons as to cl'iange their behavior under further changes of pressure, and the consequence is that such old types cannot be counted on for a perfect adjustment of current conditions. 1n the operation of this improved form of rheostat any desired means may be employed for producing the changes in pressure and position necessary for regulation of current. The device is particularly useful for the reasons above mentioned and in connection with automatic regulators where the iiuetuations in current strength or potential must be kept within as narrow limits as possible.

In Fig. 1 there is shown a preferred form of automatic dev-ice as used in connection with the improved rheostat herein described. Here the column of resistance-bodies 8 is shown in a vertical position compressed between a top abutment 15, from which said bodies are insulated, and a second insulated abutment 16, which is movable. The abutment 16 is normally pressed forward by the short spiral spring 17, which surrounds the vertical stem 18, fixed to the abutment 16 and passing downward to the motive lever 19, pivoted, as at 20. This lever 19 operates upon the stem 18 for modification of position of the abutment 16, and this is preferably accomplished by means of the lugs 2l, whose under curved surface abuts upon the nut 22 and screws on the end of the stem 18. By pressing the end of the lever 19 downward it acts through the lugs 21 and nut 22 to depress the abutment 16 and compress the spring 17. This depression of the lever 19 is accomplished in the form of device shown by means of a solenoid operating through the connecting rod 23, secured (as by screwthreads) to the center of a movable interior magnetic core 241, to the top of which is attached any desired form of retarding device, as a dash-pot 25. The solenoid-windings 26 surround a fixed interior pole piece 27,

through the center of which a non-magnetic rod 23 is carried. The downward pull of the solenoid 26 on the core 211 is opposed by a of parts shown in Fig. l is as follows: When there is no current in the solenoid 26, the action of the spring 17 aloneexerts the maximum pressure upon the column of bodies 3,

and these latter are then all lifted together against the insulated abutment 15. In this position the smallest possible resistance is offered, since all the buttons are firmly pressed together and are in multiple arc. Onl first energizing the solenoid 26 the core 24 will be depressed, thus compressing the 'long spring 28. an increasing solenoid action until the abutment 21 has been brought into contact with the nut 22, which will occur when a certain predetermined condition of balance between solenoid effect and the reaction of the spring 28 talies place. When the solenoid effect increases beyond this point, the regulating effect of the column 3 is begun, since further downward movement of the lever 19 causesa certain compression of the spring 17 and a consequent lessening of its upward pressure on the column. tions the result will be that the pressure exerted by the springs 17 and 28 will be proportionately lessened, so that the contact resistanceis increased between successive buttons, and if the action of the solenoid 26 is sufficient one after the other of' the buttons 3 (beginning at the top) will be supported by their springs 10 and being thus left behind will be virtually out of'circuit. The total resistance of the column 3 is thus gradually increased as the current in the solenoid 26 increases.

As above stated, the organization shown in Fig. 1 is intended for use in the automatic regulation of electric currents. For this purpose the solenoid 26 may occupy a variety of well-known relations to the circuits to be governed, and no particular arrangement has therefore been shown'in the drawings. The use of the long springI 28 in connection with the short spring 17 renders possible large proportional variations in pressure on the i column 3 for relatively small proportional changes in the magnetic effect of the solenoid 26. For this purpose the long spring 28 is calculated to just eounterbalance the weight of the parts within the solenoid and the righthand end of the lever 19, together with the desired normal effort of the solenoid 26. The spring 28 is made very long, so that its effort Under these latter condi- This will continue under the iniiuence of' IOO IIC

will approach that of a weight and will exert nearly constant reaction on the lever 19 independently of the actual position of said lever. It is clear that if the reaction of the spring 28 and the opposing normal action of the solenoid 26 are much larger than the actual upward thrust of the correspondingly shorter spring' 17 small changes in the percentage of effort exerted by the solenoid will correspond to very large percentages of change in the effort actually brought to bear upon the column 3. This is a very desirable condition, since it increases the degree of sensitiveness of the instrument and limits the allowable fluctuations or variations in the electric conditions which are controlled. It will be seen that even in the improved device shown in Fig. 1 the reaction offered by the column 3 itself becomes greater and greater in proportion as more buttons are lifted. Therefore equal pressure changes assume a progressively smaller significance in proportion to the total pressure exerted. In order to counteract this disturbing factor so far as possible and to tend to insure equal sensitiveness of the rheostat over all parts of its range of action, it is desirable that in proportion as the total pressure increases equal pressure increments shall produce progressively larger resistance changes. In order to accomplish this result, I have devised a form of resistance-column wherein areas of contact between the surfaces of the resistance-buttons increase upward or away from the movable pressure, such as theA abutment 16. This may be accomplished by using a variety of 'forms of resistance-body, and of these I have shown two forms in Figs. 6 and 7 of the drawings, the preferred form being shown in Figs. 7 and indicated in the illustration of the carbon buttons shown in Fig'. 3.

In Fig. 6 the carbon buttons or other resistance-bodies 3 are shown in the form of truncated cones having their larger bases upward or away from the movable compressing element. It will be seen that this arrangement insures the attainment of the objects above named namely, the progressive bringing together of larger and larger contact areas as the total pressure is increased and more and more buttons are lifted. For mechanical and commercial reasons the form of column shown in Fig. 7 is preferred, wherein carbon blocks or other resistance elements of uniform horizontal cross-section are shown, the contact-surfaces being cut away in any desired manner and according to any design. As shown in Fig. 7, less and less of the contact-surfaces are shown cut away as we consider the resistance-bodies from the bottom up. This obviously leaves more and more contact area as we proceed from the bottom up and accomplishes the ends above named.

1t is to be understood that while there has been above described a preferred form of electromagnetic regulator and preferred arrangement of the resistance-bodiesi-namely, in multiple arca preferred improved mode of operating the resistance-bodies, whereby each has its own support, and a preferred improved conformation of successive resistancebodies, whereby the contact areas increase progressively in one direction, these various improvements may be considered independently of one another in so far as my claims are concerned, although they are capable of use in one device.

It is obvious that a variety of changes in form and arrangement may be made in the above device without departing from the spirit of this invention, and the following claims are not to be limited to the details herein shown and described.

It is to be understood that my invention covers the use in the combinations claimed of resistance devices built up in any manner or made of any appropriate material.

That I claim is- 1. In a rheostat, a series of separately-supported movable resistance-bodies and means for producing' pressure at one end of the series; substantially as described.

Q. In a rheostat, a series of movable resistance-bodies, a supporting means for holding' each body away from the rest and a movable abutment at one end of the series adapted to push said bodies one against the other suceessively, substantially as described.

3. In a rheostat, a group of movable resistance-bodies connected in multiple arc with each other in the circuit to be controlled and means for producing progressive contact between contiguous bodies in said group, substantially as described.

4C. In a rheostat, a series of movable resistance-bodies, a conducting supporting' means for holding' each body away from the next, a common supporting-conductoi' for some of said individual supporting means, connected to one side of the circuit to be controlled and a second common supporting-conductor for the remaining' individual supporting means, connected to the opposite side of said circuit, substantially as described.

In a rheostat a series of resistance-bodies placed so as to tend to fall together by gravity, a yielding' support for each body, tending to hold it away from the next body and a movable abutment at the bottom of the series adapted to lift said bodies each against the next above it, beg'inning' at the bottom, substantially as described.

6. In a rheostat, a series of resistance-bodies, a yielding support for each body and a rest for said support limiting' the approach between two successive bodies in one direction, substantially as described.

7. ln a rheostat, a series of resistance-bodies, a weight attached to each, a yielding support for each body and its weight and a movable IIO abutment adapted to lift one body against the next throughout the series, substantially as described.

8. In a rheostat, a supporting-rod, a series of supporting devices and an alternate series of spacing devices, both on said rod; in combination with a resistance-body attached to each of said individual supports and means for moving said bodies toward and from each other, substantially asl described.

`9. In a rheostat, a conducting supportingrod, a series of conducting supporting devices and an alternate series of spacing devices, both on said rod; in combination with a resistance-body attached to each of said individual supports and means for moving said bodies toward and from each other, substantially as described.

10. As an element in a rheostat, a resistancebody, a yielding support therefor attached at one end thereto and a stop upon which said support rests, substantially as described.

11. As an element in a rheostat, a resistancebody, a curved spring attached at one end to said body and a plate attached to the opposite end of said spring and forming a rest for the same, substantially as described.

12. As an element in a rheostat, a yielding support, a resistance body, a Weight, and means for attaching said Weight and resistance-body to said support, substantially as described.

13. As a support for resistance elements in a rheostat, a plate bent at an angle and a pair of springs attached to said plate on one side of the bend and so curved as to rest upon the edge of the other bend in said plate, substantially as described.

14. In a rheostat, a series of resistancebodies adapted to be brought into contact With each other and provided with contact-surfaces of progressively-different areas ,from one end of the series toward the other, substantially as described.

15. In a rlieostat, a series of resistancebodies each of which has a contact-surface turned toward the next, one surface of each being holloWed out at one part to prevent contact With the next body along that part, substantially as described.

16. In a rheostat, a series of resistancebodics, normally placed close together in a line, the contiguous surface of said bodies being hollowed out so as to leave contact-surfaces of progressively-dilerent area from one end of the series toward the other, substantially as described.

17. Ina regulator for electric currents, a series of resistance-bodies, a primary spring for exerting pressure thereon, a lever for exerting pressure on said spring, a solenoid attached to said lever for its operation and a balancing-spring opposing the eort of said solenoid and so proportioned as to suffer a smaller proportionate change in its total reaction than occurs in said primary spring for a given change in position of said lever, substantially as described.

18. As an element in a rlieostat, a resistancebody, a yielding support attached thereto and a stop for said yielding support, substantially as described.

19. In a rheostat, a series of resistancebodies adapted to be brought into contact with each other and provided with contact-surfaces of progressively-different areas from one part of the series toward the other, substantially as described.

20. In a regulator for electric current, a series of resistance-bodies, a primary springfor exerting pressure thereon, a solenoid connected to said spring and adapted to exert pressure thereon, and a balancing-spring opposing the effort of said solenoid and so proportioned as to suffer a smaller proportional change in its total reaction than occurs in said primary spring for a given change in position of said solenoid, substantially as described.

' MONTGOMERY VADDELL. I/Vitnesses:

CHARLES F. VVArrE, WILLIAM H. KETTRA. 

